[Exim] Invalid Sender: headers

Since I moved from exim-4.12 to 4-14 early last month I have had a significant
number of complaints that e-mail is no longer getting to some of our users.
Messagers are being rejected "Administrative prohibition" because they have
unqualified addresses in the Sender: (eg "Sender: abc1"). This is as noted in the
ChangLog.

(I have a acl_smtp_data acl containing require verify = header_sender.)

Are others experiencing the same? I presume so.

My problem is that the rejection message is so uninformative (Administrative
prohibition) and I get the job of tracking the problem in the rejectlog to see what
the specific problem was. I don't see how I can use message in the ACL to report
the reason because I can't tell whether it is the Sender:, Reply-To: or From: header
which has generated the failure.

Phil.
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Phil Chambers (postmaster@???)
University of Exeter